Mr Trump reopened old wounds over Greenland on the eve of the meeting by insisting that the US should control the semi-autonomous territory.
“Denmark doesn’t spend money to really help Greenland, but it’s an important part for the US, and it’s surrounded by China ships and Russian ships … [It] should be controlled by the US, not by Denmark,” Mr Trump said.
In response, Ms Frederiksen said: “We hope that all, including all allies, will respect the Greenland people’s right for self-determination. We are sovereign states, and we need everybody to respect our territorial integrity and our sovereignty.
“One of the reasons why we have built Nato many, many years ago, is if anything happens to one of us, then everybody should stand up for each other.”
Kristrún Frostadóttir, Iceland’s prime minister, said Greenland “belongs to the people of Greenland” and called for unity among Nato allies in the face of external dangers.
“We have threats coming from outside the alliance,” said Ms Frostadóttir. “Russia is their biggest threat when it comes to these Nato allies. We need to focus on us and how we stick together.”